The present invention relates to a drive control device for controlling a zoom lens of a camera. More particularly, the invention relates to a drive control device for controlling a zoom lens of a camera comprising: a zoom lens assembly comprising zoom lenses arranged on an optical axis; a drive means comprising a motor for driving the zoom lenses along the optical axis; a first control means for controlling a first zooming function of the camera wherein the zoom lenses are moved at a relatively slow normal speed to continuously change the focal point of the zoom lens assembly; and a first trigger means for carrying out the first zooming function only when the drive means is being manipulated.
Various kinds of electrically driven electronic cameras have been developed and commercialized. With such an electronic camera, a user can set the focus point of the zoom lens on an object positioned at any distance from the longest distance to the shortest distance only by manipulating buttons of the camera. Therefore, the user can easily compose an image of the picture as desired by viewing the field through a finder of the camera. The prior art camera is constructed in such a way that a zooming function is continued as long as the user presses a zoom button for starting the zooming function and changing focal length of the zoom lens and stopped when the button is released. In other words, the user manipulates the zoom button while viewing an object to be taken as a subject of the picture through the finder, the size of the object through the finder being continuously changing. The user stops the manipulation of the button when the size of the object (or composition) becomes as desired. For this purpose, the drive motor must drive the zoom lens at a relatively slow speed enabling the user to view and judge the optical zoom position of the object. Also, the zoom focusing movement must immediately stop when the composition or the angle of field becomes as desired without overrunning. From this point, the drive motor must drive the zoom lens at a relatively slow speed.
However, in some cases depending on the object of the photograph, the user requires the composition image of only the longest focal distance (referred to as "teleposition" below) or the shortest focal distance (referred to as "wide position" below) without requiring the continuous change of the angle of field in the range of intermediate distance. Also, in this case, the user requires the zoom lens be changed quickly as possible from the teleposition to the wide position and vice versa. One of such cases is, for example, when a scenery of fireworks is to be taken as a subject of the picture wherein the cameraman wishes to take an entire scenery of the fireworks and zoomed shots of parts thereof as well before the fireworks are extinguished. In such a case, with the prior art camera which zooms the object at a slow speed, the timing of taking a shot is often late so that a desired shutter chance is missed or a desired composition can not be obtained.
Also, a skilled person often uses the camera as a two focal point camera in which he or she uses only the teleposition and the wide position and in which the teleposition image and the wide position image are repeatedly changed for confirmation of the effect of the zoomed image. In such a case, it is desirable that the teleposition image and the wide position image are quickly changed. However, with the prior art zoom lens system, the zooming movement is slow so that the user must wait for some time until the image is changed manipulating the zoom switch (usually pushing the zoom button).
On the other hand, for a person who is not skilled in manipulating the zoom camera, it is troublesome to manipulate the zoom switch for functioning the zoom lens system so that the zoom lens system is not fully mastered and handled.